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Two Bandwidth Packing Algorithms for the Centralized Wireless Network and Their Average-case Analysis

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Journal of Shanghai Jiaotong university(Science) 2007年第3期12卷 397-404页

作者：陈建新龚玲杨宇航曾鹏 dept. of electronic eng. Shanghai Jiaotong Univ. dept. of Computer eng. of Nanjing Univ. of Posts & Telecommunications

This paper presents a detail analysis of two bandwidth packing algorithms, used for processing connection requests in the centralized wireless network. Each call comes with a specific bandwidth request. A request can be satisfied only if there is sufficient bandwidth available during resource scheduling and allocation. Unsatisfied requests were held in a queue. The metric of bandwidth utilization ratio was used to quantify the performance of our algorithms. By theoretical analysis, our algorithms can improve the average bandwidth usage ratio significantly, about 8%~10% without adding much computation complexity. Moreover, our algorithms outperform next fit with fragmentation (NFF) algorithm when the bandwidth resource is scarce. In this paper, the contributions follows: Introducing bandwidth packing problem into wireless network; Proposing two new bandwidth packing algorithms for wireless network where the complicate scheduling algorithms are prohibited; Studying the average performance of our algorithms mathematically, which agree well with the simulation results.

关键词： wireless network average performance bandwidth packing problem (BWP)

Influence of Error-prone Channel on the Performance of IEEE 802.11 WLAN Utilizing RTS/CTS Handshaking

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Journal of Shanghai Jiaotong university(Science) 2007年第6期12卷 799-804页

作者： Haider M. AlSabbagh 陈建平徐友云 dept. of electronic eng. Shanghai Jiaotong Univ.

A comprehensive study was presented for WLAN 802.11b using error-prone channel. It was theoretically and numerically evaluated the performance of three different network sizes with the bit rates that available in 802.11b protocol. Results show that throughput does not change with the size of the network for wide range of bit error rates (BERs) and the channel bit rates play a significant role in the main characteristics of the network. A comprehensive explanation has given for the phenomenon of the packet delay suppression at relatively high level of BERs in view of the size of the networks and the BERs. The effect leng.h of the transmitting packets is also investigated.

关键词： IEEE802.11b request to send/clear to send(RTS/CTS) wireless local area network(WLAN) error-prone channel

Research on Oil/Gas In-pipe Inspection Robot

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Journal of Shanghai Jiaotong university(Science) 2005年第3期10卷 221-225页

作者：宋一然颜国正徐小云 dept. of electronic and Information eng. Putian Univ. Putian 351100 China School of electronic Information and Electrical Eng. Shanghai Jiaotong Univ . Shanghai 200030

A new type of in-pipe mobile robot was designed and developed on the basis of w heel in-pipe robot and crawler in-pipe robot. The three sets of driving wheels circumferentially 120° apart in the cross section, both front and rear driving wheels are distributed on the same parallelogram mechanis m. The driving motor drives the three sets of driving wheels by worm couple, the regulating motor makes the three sets of driving wheels push against the pipe inwall with stable and adequate pressing force by the ball screw pair and p ressure sensor, so the in-pipe robot can provide adequate and stable traction force. The robot mechanism is simple and sm all in size and work reliably . It is particularly suitable to the pipe with diameter 400～650 mm.

关键词： in pipe robot parallelogram machanism pipe inspection

Research on Miniature Hexapod Bio-robot

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Journal of Shanghai Jiaotong university(Science) 2005年第3期10卷 226-230页

This paper described the structure and control of a new kind of miniature hexap od bio-robot, analyzed the moving principle of the robot. The robot is based on the principle of bionics, its structure is simple, design novel, unique. It can mov e forwards and backwards. The external dimensions of bio-robot is: leng.h 30 mm , width 40 mm, height 20 mm, weight 6.3 g. Some tests about the model robot were made. The experimental results show that the robot has good mobility.

关键词： hexapod robot bionic robot link curve atlas gait control interface

A Direct Compensative Robust Optimal Control (DCROC) Law for Ship Straight-line Track-keeping

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Journal of Shanghai Jiaotong university(Science) 2007年第3期12卷 364-369页

作者：李文魁田蔚风周岗陈永冰周永余 dept. of Instrument Science & eng. Shanghai Jiaotong Univ. School of electrical and Information eng. Navy Eng. Univ.

A linear quadratic optimal direct track-keeping control law was proposed based on first-order Nomoto nominal model. Furthermore, based on Lyapunov stabilized theory, considering parametric uncertainty from variations of ship speed and disturbances uncertain from wind, wave and sea current, a direct compensative robust optimal control (DCROC) law was developed. It can guarantee closed-loop system globally and uniformly converge to a remained set. High accuracy and robustness were achieved. By introducing some nonlinear blocks, closed-loop system achieves global and uniform asymptotical stableness. Numerical simulations on a Mariner Class ship are presented to validate the control law.

关键词： ship track-keeping direct compensative robust optimal control (DCROC) Lyapunov stability

Cryptanalysis of Two Pseudo-attacks from the Same Mathematic Mistake

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Journal of Shanghai Jiaotong university(Science) 2007年第3期12卷 394-396页

作者：刘杰施建俊李建华 dept. of electronic eng. Shanghai Jiaotong Univ.

Yang and Shieh proposed a timestamp-hased password authentication scheme. Fan and Shen gave differ- ent improvements on it. Wang claimed that Fan＇s improvement is insecure and gave his attack. Yang did the simi- lar things on Shen＇s scheme. This paper gave further cryptanalysis on Wang＇s and Yang＇s attacks and pointed out that both of their attacks are infeasible. Wang and Yang made the same mathematic mistake and their attacks are pseudo.

关键词： password authentication cryptanalysis number theory

A New AgMeO Contact Material

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Journal of Rare Earths 2001年第2期19卷 145-148页

作者：王景芹陆俭国温鸣王宝珠唐红梅吕玉申 dept. of electrical eng. Hebei Univ. of Technol. Tianjin 300130 China

A new silver rare earth oxide contact material, Ag/La2O3(12), was produced by powder metallurgy method. Its performances are as follows: the density is 9.71 similar to 9.96 ***(-3); the hardness (HB) is 760 similar to 970 MPa and the resistivity is 2.25 similar to 2.38 mu Omega . cm. The microstructure of Ag/La2O3(12) mas analyzed by SEM and EDS. Rare earth oxide La2O3 shows two shapes, which are uniformly distributed in the form of sphere and abnormality in Ag matrix. La2O3 shows fine spherical shape in the melted area of Ag after laser acting which is used to simulate electric are. The results are contributed to the less splash erosion of Ag. Compared with the main physical and mechanical properties of Ag/SnO2(12) and Ag/CdO(12), the properties of three contact materials are similar, and hence Ag/La2O3(12) may become a potential contact material to be used as the substitute of Ag/CdO(12).

关键词： rare earths contact material silver rare earth oxide powder metallurgy microstructure

Predicting the Dielectric Streng.h of c-C_4F_8 and SF_6 Gas Mixtures by Monte Carlo Method

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Journal of Shanghai Jiaotong university(Science) 2007年第1期12卷 121-124页

作者：吴变桃肖登明 dept. of electrical eng. Shanghai Jiaotong Univ.

An improved Monte Carlo method was used to simulate the motion of electrons in c-C4F8 and SF6 gas mixtures for pulsed townsend discharge. The electron swarm parameters such as effective ionization coefficient, -↑α and drift velocity over the E/N range from 280～700 Td（1Td=10^-21 V·m^2） were calculated by employing a set of cross sections available in literature. From the variation cure of -↑α with SF6 partial pressure p, the limiting field （E/N）lim of gas mixture at different gas content was determined. It is found that the limiting field of c-C4F8 and SF6 gas mixture is higher than that of pure SF6 at any SF6 mixture ratio. Simulation results show excellent agreement with experiment data available in previous literature.

关键词： c-C4F8 and SF6 gas mixture Monte Carlo limiting field dielectric streng.h

ID-Based Authenticated Dynamic Group Key Agreement

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Journal of Shanghai Jiaotong university(Science) 2005年第3期10卷 236-241页

作者：王莺洁潘军诸鸿文 dept. of electronic eng. Shanghai Jiaotong Univ. Shanghai 200030 China

Two ID-based authenticated group key agreement schemes, proposed by Choi et al and Du et al, are insecure against an impersonation attack and th ey only discussed the static group. This paper proposed a variant of BD protocol , which is fully authenticated by a proven-secure ID-based signature scheme. T he protocol can res ist the impersonation attack, and other security attributes are also satisfied. Compared with Choi et al and Du et al schemes, the proposed one is mor e efficient and applicable for dynamic groups.

关键词： group key agreement elliptic curve authentication ID-based signature